Maricultured Fish ?

[Anonymous]

Hi,guys! I know there are alot of people here who know a ton, so I wonder if you help me understand something?

Is an ocean raised fish less healthy than one raised in a sterile, bb system? This thread came up elsewhere but I feel the "experts" there can't discuss it because it might hurt the bottom line. I dunno, but I want to understand this theory...

Raising a fish in pen next to the shore would be where the water is most contaminated but still?

Enlighten me?

http://forum.marinedepot.com/Topic74994-14-1.aspx

 

[Anonymous]

OK, let me rephrase.

Has anyone here heard of raising fish in net pens in the ocean, then selling them to the aquarium trade? Getting larvae or fry and then raising them in the ocean in a pen?

 

[Anonymous]

Of course. Most of our baby leopard groupers are pen raised.

 

[Anonymous]

So, I wonder about the promoters of this theory, that CB seahorses are healthier than net penned. Could it be similar to theory that GW is bogus promoted by researchers who work for Exxon?

Hmmm

 

[Mthompson]

There are different levels of aquaculture systems, referring to the extent that the human needs to care for the individuals.

intensive - keeping fish (often indoors) from young through to adulthood. This requires the human to provide all the requirements an organism needs to survive. This is also the most expensive

semi-intensive - a mix of both of the other two. An example would be U.S. catfish production in farm ponds. The fish get food from the farmer and also natural food from the pond

extensive - this is usually taking larvae, fry, or fingerlings and placing them in a natural environment in some form of cage or pen. There is usually little input from the human part, until harvest time. This the least expensive.

There are pros and cons for each of these systems. Most notably for marine ornamental production is that difficulty in feeding larvae. Marine fish need high levels of omega-3 and omega-6 fatty acids in the diet. This if best and easily supplied using live feeds, however, production of live (or artificial) feeds for marine larvae if very difficult. So this is one reason to put them in the ocean, where live feed is relatively abundant. As more studies are completed to figure out the specific nutrient requirements of the marine larvae, more and more intensive culture can ensue.

Hope this helps somewhat. If you have any more questions I can try to explain or point you towards some readings.

 

[Anonymous]

Really? That would be great!

In your opinion, would a fish raised in an extensive system be healthier than the same species raised in an intensive system? or visa versa?

 

[Mthompson]

This is a very complex question, since there are many many variables involved with each species.

One of the drawbacks to intensive systems is that they generally have higher densities, which often times leads to higher incidences of disease. However, if the diseased are treated properly and promptly, then this might increase the organisms' resistance to future exposure to that disease.

A plus to using intensive culture is that the organism will be more suited for aquarium use. This is because the organism is going to be 'used' to the higher densities, human interaction (feeding, watching, etc.), and general boundaries of an aquarium.

This can be seen when you compare many freshwater fish (mollies, for example) with wild captured marine fish. Mollies are several generations intensively cultured; so-much-so that they are almost domesticated in a sense. When comparing mollies to hawkfishes, the hawkfish will continually hunt for food when first introduced to a captive environment (your home aquarium). This behavior can be seen for several weeks or longer, as it slowly acclimates to the routines of captivity. The molly, on-the-other-hand, will almost instinctively know that you mean 'food is coming'; as is evidenced by their continual nosing on the glass while you stand there (as opposed to the hawkfish hunting all the time and hiding when you are there).

Interesting (to me at least) is that this same type of behavior can be demonstrated using wolves (raised by humans from pups) and domestic breeds of dogs. I know this is off subject, but when faced with meat inside a cage that the animal cannot reach, the dog will look at the meat and then turn to its owner for help. The wolf, will look at the meat and then start trying to figure out how to get it on its own (even though its 'owner', who has raised it since birth, is sitting right there).

Back to your original question...finally :roll: ...if you are talking about if it is better or more healthy for a marine ornamental (this is a key component) to be raised intensively or extensively; my answer is - intensively, as long as the nutrient requirements can be satisfied and there is no other limiting factor(s) causing undue problems (stress of the organism, high costs, etc. - which is often the case or there would be no wild caught fish)

 

[Anonymous]

Thanks! Where did you learn so much about this?

 

[Mthompson]

I have a B.S. in Fisheries Biology and am currently working on my M.S. in Aquaculture, in which I am studying fish nutrition. In my studies, I have to read a lot of papers and write/present a lot of my own writings. Luckily, most of the topics can deal with whatever I am interested in, so I choose to do a lot on marine ornamental stuff. I do have an unfair advantage over most hobbyists though, in that I have ready access to almost any scientific journal or publication, as well as conference proceeding and other presentations. On the down side (as I see myself as a realist), I tend to look at everything from my a scientific standpoint; and this often inhibits or hinders the enjoyment we get out of keeping aquatic organisms.

Someday I hope to use my knowledge to help this industry wean itself off of its reliance on natural stocks (of fish and invertebrates); which we all know are plummeting and are in dire need of some serious relief from our misuse. I feel strongly about the the need for connectedness and openness among science, industry, and hobbyists in order for needed advances, policies, and standards to have any effect. Unfortunately, we are not there yet...but someday we will be.

I would be glad to answer any other questions you have about any aspect of this hobby of ours. I am also willing to share whatever articles or papers I have.

Take care,

 

[Anonymous]

OK, a few specific questions?

I am totally into seahorses so I want to direct it that way?

OK, so here is what I know about this genus:

Raising a s SH fry in captivity means you will have to grow millions of copepods to feed it it's natural diet. But, breeders do not do that because I think it is too impossible? They use enriched baby brine shrimp. In my experience, I have tried both feeds. With the BBS, the fry do not live long. The ones fed copepods (TiggerPods, thank you Reed Mariculture and Reefpods, thank you Algagen) live and go on to reproduce.

Raisning them in the ocean, they would get the natural diet.

Would that increase their immune systems to be less susceptible to our aquarium environments bacteria?



Also, would a ocean raised seahorse have more parasites and bacterial issues than a sterile tank raised? Or would having exposure to these things give them immunities?

 

[Mthompson]

The area of marine larval nutrition is relatively unknown. There is also no better source of nutrition than the natural diet of an organism, seahorses in this case. I know of a few published papers that deal specifically with feeding enriched brine shrimp to Hippocampus spp. There is more to feeding marine larvae than just the natural prey species, since captive rearing of the prey can also result in deficiencies in the prey itself which will transfer to the primary organism. This is why larvae tend to do much better in ocean net pens or cages.

As for the immune system...

There are basically two types of immune responses, specific (or adaptive) and non-specific (or innate). The specific immune response is what most people think of first. It consists of many different types of components that protect against a specific pathogen, and also forms antibodies for specific antigens of pathogens after they are encountered. In a sense, the specific immune response is a way to ensure that you don't catch again what you just had. On the other hand, there is the non-specific immune response. This consists of different types of components (lysozyme and complement for example) that roam around the body, continually fighting off invaders (via phagocytosis or some other method). The two systems combine to make an impressive defensive array.

This synopsis is extremely brief, however, as people make entire careers of just one tiny aspect of this complex system. It is also very important to note that diet has a large effect on the immune response of organisms. For example, omega-3 fatty acids increase inflammation and immune response, whereas omega-6 fatty acids decrease inflammation and immune response. Both of these types of fatty acids are dietary requirements of all aquatic organisms. Furthermore, phospholipids are required in the diets of marine larval fish and invertebrates (which also require cholesterol). All of these requirements can have an effect on the immune response of organisms, so it is not as simple as what they are exposed to while growing up, but providing their requirements will definitely aid in their survival and overall health.

The seahorses raised intensively could have more or less problems with parasites, bacterial infections, etc. depending on the conditions they are raised. There is an article by C.M.C. Woods (2003) that shows an increase in survival and growth rate of juvenile Hippocampus abdominalis in systems that are equipped with UV sterilization. This same study also showed difference among Artemia, cyclop-eeze, and another diet. Obviously in intensive culture systems it is much easier to diagnose and treat various diseases, and if done properly, this practice should result in healthy organisms.

In either culture system (intensive or extensive) you can have unhealthy sick individuals (tanks are never sterile when in use). The difference is that the ease of diagnosis and treatment is much greater and more effective in the intensive system. This system, in turn, adds costs (or value depending on your viewpoint) to the organisms being cultured.

I tend to feel that if someone is going to spend the time and money intensively culturing an organism, they will most likely take necessary steps to ensure that the health of the organism is maintained. Then again, there are those bad apples out there....

 

[Anonymous]

Holy mother load of info! Thanks!

So, immune systems in fish are very similar as in humans? T-cells, neutrophils, esinophils, ect?

I so want to be an ichthyologist!

 

[Mthompson]

Well, they are not exactly the same, but they are similar. Aquatic organisms tend to rely more on the non-specific immune response, but they do have a specific response. I get to study and play with this a bit with my thesis work! It is pretty fun, but the writing part is not so much fun (doing that right now ).

BTW, Ichthyology(-ist) is a general term for the study(-ier) of fish, so you better narrow your goals down a bit. :wink: (but it is a blast any way you slice it) If you want to do it, go ahead....There is plenty of room out here for many many more people. Plus you already have the passion, all you need is the training!

 

[croaker]

MT,

What is a good source of omega-6 fatty acids for larval fish?

 

[PeterIMA]

To SeahorseWhisperer,

Your question was whether there are people rearing MO fish (either from eggs or post larvae) in net pens for export to the aquarium trade? The answer is that there are several groups doing this.

About a year ago on RDO, I described the hatchery growout program established by EASTI near Bacacay in Albay Province, Philippines. Unfortunately, the hatchery was destroyed by a typhoon.

There are other programs like this in the Philippines. Right now, I can obtain blue tangs reared in cages in Osamis, Philippines. The pricing is less than for wild caught blue tangs.

There is also a similar program (not run by EASTI) in Lombok, Indonesia.
So, with the right knowledge and skills it is feasible.

Peter Rubec

 

[Mthompson]

The fatty acid requirement of fish is the most variable component of the diet between different species. All aquatic organisms need n-3 and n-6 fatty acids preformed in the diet, as they lack the ability to make them (or make them at a fast enough rate). The differences appear when you look at what type of n-3 or n-6 is needed specifically (e.g.- mono-, poly- or highly unsaturated). Different types of fish (e.g.- carnivore, omnivore, marine, freshwater, etc.) have different abilities to elongate and desaturate fatty acids, making the different forms of fatty acids. It is also important to note that it is not just a strict level of each type, but what seems to be more important is the ratio of n-3:n-6 in the diet; too much of one is just as bad as not enough.

Omnivores - generally only require polyunsaturated fatty acids (e.g.- linoleic or n-6 and linolenic acid or n-3) as they can elongate and desaturate fatty acids fairly easily, but more energy (fatty acids) is required to do so. Good sources for both of these can be found in canola, linseed, and soybean oil. If you are looking for just n-6, then corn oil (~58% n-6), cottonseed oil (~51% n-6), safflower oil (~74% n-6), and sunflower oil (~66% n-6) make a better choice because they are lower in n-3.

Carnivores - generally require highly unsaturated fatty acids (HUFA) (e.g.-eicosapentaenoic or n-3, docosahexaenoic or n-3, and arachidonic acid or n-6) because most lack any ability to elongate and desaturate fatty acids. This creates a problem, because the only source of HUFA's is fish oils, which are expensive and harm the environment by taking many fish out of it. The best source of n-6 HUFA's can be found in cod liver oil (~1.6% n-6 HUFA). Another source would be menhaden fish oil (~0.2% n-6 HUFA).

Croaker, I am not sure if this answered your question or just made it all more confusing. What fish are you working with? Or, if you need a different question answered now...just shoot and I will do my best.

 

[croaker]

Thanks MT, that did answer my question. I'm working with seahorses right now actually. I was mostly just curious about the differences and you answered it perfectly.

Thanks for the info!

 

[midgetwaiter]

I have a question for MT about fatty acids that are are commonly advertised as an ingredient in commercial foods and supplements.

Many studies in humans show a very big gap in the effectiveness of omega 3 and 6 supplements that have some pretty big implications. Basically those made with whole fish oils and such have been shown to be much more useful than those made with vegetable ingredients like flax seed oil. Are you aware of any similar studies done with an aquaculture POV? Does one source prove much more effective than others?

I'm just sort of curious so if you know off the top of your head that would be cool but please don't spend a ton of time on it or anything.

 

[Mthompson]

No problem croaker, just let me know if you need more info, or would like me to point you to some hard copies of literature.

midget, there are some very fundamental differences between the n-3 and n-6 fatty acids from plant and animal sources. I will try to summarize the main differences below as it pertains to aquaculture (but this somewhat explains the differences for human use as well). As for humans, it has also been shown that obtaining these essential fatty acids (EFA's) from the source itself, by eating tuna or salmon for instance, is more effective than taking fish oil supplements. It is not clear yet, but there seems to be some difference in usefulness in terms of the way they are supplied; perhaps something like the combination of amino acids from the protein along with the fatty acids - many studies need to be done to draw out these questions though.

There are many many studies done in aquaculture looking at the effectiveness of different EFA sources. All fatty acids are composed of the same basic structure, a carbon chain and a carboxylic head group (fig 1). We know that there are key structural differences between plant and animal sources, specifically the length of the carbon chain (number of C atoms) and the number of double-bonded carbon atoms in that chain (degree of unsaturation - the more double-bonded carbons, the more unsaturated the fatty acid). There is also levels of unsaturated, 1 double- bond = monounsaturated, 2 or 3 double-bonds = polyunsaturated, and 4+ double bonds = highly unsaturated. The 'omega' distinction is derived from the position of the first double bond on the C-chain from the methyl end (e.g.- omega-3 fatty acids have the first double bond between the 3 and 4 carbons from the methyl end (fig. 2 - see also for nomenclature of fatty acids).

With that said, the differences between plant oil and fish oil source fatty acid profiles iare as follows:

plant sources - generally shorter-chain mono- and polyunsaturated. Linoleic acid (18:2n-6) and linolenic acid (18:3n-3) are the two essential fatty acids found in plant sources. There are others (18:0, 18:1, 20:1, etc.), but linoleic and linolenic are the EFA's because they have the n-3 and n-6 double bonds, which most organisms cannot synthesize. However, many omnivores have evolved to utilize these sources (since they ingest them), so they have the enzymes elongase and desaturase in their body to both add carbons (elongase) to the chain (two at a time at the carboxylic end) and create double bonds (desaturase) in the chain (just not at the n-6 and n-3 positions). This means that we can substitute plant oil for fish oil in certain species (i.e.- omnivores) that have this ability, as they can synthesize (make) the highly unsaturated n-3 and n-6 fatty acids with the proper building blocks.

fish sources - these contain the long-chain highly unsaturated fatty acids preformed, but they also contain some of the short-chain mono- and polyunsaturated fatty acids too. The three main EFA's available in fish oil sources are arachidonic acid (AA; 20:4n-6), eicosapentaenoic acid (EPA; 20:5n-3), and docosahexaenoic acid (DHA; 22:6n-3). Carnivores have evolved feeding on lower species, that coincidentally contain these EFA's preformed, thus carnivores have lost the ability to synthesize them. In other words, they need the long-chain highly unsaturated fatty acids preformed in their diets.

I can give specific examples of study results if you want, but there are so many that I would need to know what species you want me to tailor it towards. However, most of these studies deal with food fish rather than ornamentals, but the same conclusions can be applied to most of the species in these broad categories. And if you want to be on the safe side, you can use fish oils exclusively and be just fine (it is just a lot more expensive).

 

[Anonymous]

Ok, now I need to get specific! (actually much less specific because I am blonde!).

I really want to know if the theory that CB seahorses raised in sterile conditions are hardier, healthier than those raised in net pens in the ocean. So, can I just ask a few simple ( but already answered?) questions?

First, nutrition:

Net penned fish raised in the ocean would have their natural foods available, but because of the confines of the pen, would they have less food available. They would get excellent food but maybe less.

CB fish raised in sterile conditions would get enriched artemia. In my experience, it is very hard to feed only BBS with it's yolk sac intact, so the nutrition is provided by Selco products.


Which of these two nutritional sources would produce the healthiest fish?